Photopolymerization-based 3D printing has emerged as a key technology in hydrogel manufacturing, broadening the attributes of hydrogels and extending their applications into diverse engineering fields. However, the mechanical properties of hydrogels dramatically impact the functionality and quality in practice. It is necessary to develop an appropriate theoretical model to predict the evolution of the mechanical properties of hydrogels during the photopolymerization process. In this work, systematical experiments were performed to investigate mechanical properties of PAAm hydrogel under different photopolymerization condition. The results reveal a noticeable increasement in both elastic and viscous behavior of hydrogel with the advancement of polymerization. To fully capture the experimental observations, we developed a coupled photo-chemo-mechanical theoretical framework that integrates reaction kinetics with a physically-based viscoelastic constitutive model. Within this model, the degree of conversion serves as an internal variable, which related to microscopic structures such as correlation length, and tube diameter. The developed model exhibits remarkable prediction ability for hydrogels with various degree of polymerization. The current work paves a potentially new avenue for understanding the evolution of mechanical properties in photopolymerized hydrogels, providing theoretical guidance for the manufacturing of hydrogels through photopolymerization-based 3D printing.

中文翻译：

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基于光聚合的3D打印水凝胶的光化学机械耦合本构模型


基于光聚合的3D打印已成为水凝胶制造的关键技术，拓宽了水凝胶的属性并将其应用扩展到不同的工程领域。然而，水凝胶的机械性能极大地影响了实践中的功能和质量。有必要开发合适的理论模型来预测光聚合过程中水凝胶机械性能的演变。在这项工作中，进行了系统的实验来研究不同光聚合条件下PAAm水凝胶的机械性能。结果表明，随着聚合的进展，水凝胶的弹性和粘性行为显着增加。为了充分捕捉实验观察结果，我们开发了一个耦合的光化学机械理论框架，将反应动力学与基于物理的粘弹性本构模型相结合。在该模型中，转换程度作为内部变量，与相关长度、管径等微观结构有关。所开发的模型对不同聚合度的水凝胶表现出显着的预测能力。目前的工作为理解光聚合水凝胶机械性能的演变开辟了一条潜在的新途径，为通过基于光聚合的3D打印制造水凝胶提供了理论指导。